1. Field of the Invention
The present invention relates to a small form factor optical/magnetic disk for information storage, and more particularly, to a small form factor optical/magnetic disk having a metal hub.
2. Description of the Related Art
In general, information storage devices, for example, disk driving devices, are required to have small form factors in order to meet the requirements of small electronic systems. Also, optical or magnetic disks used for information storage devices are now designed to be detachable in order to increase user convenience and achieve easy transfer of information.
A small form factor optical/magnetic disk having a diameter of approximately 1 inch has a metal hub attached to a central portion of a disk plate. The optical/magnetic disk is rotated about a spindle motor shaft, which is coupled to the center of the metal hub, for reading or writing of information. It is known that a process of attaching the metal hub to the central portion of the disk plate is the most difficult process in manufacturing the small form factor optical/magnetic disk.
FIG. 1 is a cross-sectional view of a conventional small form factor optical disk 10 disclosed in U.S. Patent Publication No. 2003/0157292 issued to DataPlay, Inc.
Referring to FIG. 1, the small form factor optical disk 10 includes a metal hub 16 installed around a central hole 14 of a disk plate 12 to couple the small form factor optical disk 10 to a spindle motor shaft (not shown) of an information storage device to rotate at high speed.
The metal hub 16 protrudes over and under the disk plate 12. The metal hub 16 includes a metal plate 18 and an intermediate plate 20. The disk plate 12 and the intermediate plate 20 are made of polycarbonate. The metal hub 16 is attached to the disk plate 12 by first coupling the metal plate 18 and the intermediate plate 20, precisely aligning the coupled metal plate 18 and intermediate plate 20 around the central hole 14 of the disk plate 12, and attaching the coupled metal plate 18 and intermediate plate 20 to the disk plate 12. The intermediate plate 20 of the metal hub 16 is attached to the disk plate 12 using an epoxy.
Since the metal hub 16 is formed by stacking the metal plate 18 and the intermediate plate 20 around the central hole 14 of the disk plate 12, the thickness of the central portion of the optical disk 10 increases greatly. As the thickness of the central portion of the optical disk 10 increases, the height of the spindle motor shaft for rotating the disk 10 increases and the overall thickness of the small form factor information storage device 10 increases as well.
Also, the small form factor optical disk 10 of FIG. 1 has a drawback of high manufacturing costs since the process of attaching the metal hub 16 to the disk plate plate 12 is complicated as described above. The small form factor disk 10 of FIG. 1 has a further problem in that it is difficult to precisely align and attach the coupled metal plate 18 and the intermediate plate 20 around the central hole 14 of the disk plate 12.
FIG. 2 is a cross-sectional view of a conventional disk 30 disclosed in U.S. Pat. No. 5,947,024 issued to Sharp. The disk 30 includes a disk plate 32 and a disk hub 34. The disk hub 34 includes a main body 36, a flange 38 formed along an edge of the main body 36, an energy director 40 installed under the flange 38, and a central hole 42 formed in a central portion of the main body 36. A magnetic plate 44 is installed in the main body 36. The disk hub 34 is attached to the disk plate 32. When the disk hub 34 and the disk plate 32 are coupled to each other, the disk plate 32 and the energy director 40, which is made of a hard synthetic resin, are attached to each other using an ultrasonic process.
Since the disk 30 of FIG. 2 is housed in a cartridge case and the central portion of the disk hub 34 is also thick, it is difficult to realize the disk 30 of FIG. 2 as a small form factor disk.